1. Field of the Invention
The present invention relates to an optical scanning apparatus for optically scanning a surface to be scanned, and an image forming apparatus such as a copy machine and a printer provided with the optical scanning apparatus.
2. Related Art
In an image forming apparatus such as a copy machine and a printer, a surface of an image carrying body is uniformly charged by way of a charging device, and the image carrying body is scanned by an optical scanning apparatus. As a result, an electrostatic latent image corresponding to image information is formed on the surface of the image carrying body. Thereafter, the electrostatic latent image is developed by way of a developing device using a toner as a developer, and is visualized (developed) as a toner image. The toner image is transferred onto paper by way of a transfer device, and then the paper is heated and pressurized by way of a fixing device, a result of which the toner image is fixed onto the paper. The paper with the toner image fixed thereon is ejected outside the apparatus, thereby terminating a series of image forming operations.
Incidentally, an optical scanning apparatus, which optically scans an image carrying body and forms an electrostatic latent image on a surface thereof, is positioned and fixed to a metal frame of an image forming apparatus. Moreover, the optical scanning apparatus is configured by accommodating optical components such as various lenses and mirrors, a polygon mirror (rotating polygon mirror) as a deflection means, a polygon motor that rotationally drives the polygon mirror, etc. in a housing made of resin.
When the number of sheets of paper to be printed is increased in the image forming apparatus provided with the optical scanning apparatus, the ambient temperature inside the housing is increased due to heat generated by revolution of the polygon motor, and thermal deformation occurs in the polygon mirror. This adversely affects a focal length and the like, thereby making it impossible to perform optical scanning with high precision. This brings about problems such as deterioration of image quality.
Accordingly, for example, Japanese Unexamined Patent Application, Publication No. 2008-268698 suggests a configuration including a blower that generates an air flow, and an air-duct that guides the air flow from the blower, inside a housing of an optical scanning apparatus.